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Research Article

Hybrid Deep Learning with Attention-Based Interpretability for PM2.5 Forecasting in Delhi Urban Environments

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DOI:

10.3791/71004

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August 7th, 2026

In This Article

Summary

CORTA (Correlation Optimized Ranked Transfer-Attention)-Net, a hybrid deep learning framework for short-term PM₂.₅ forecasting in Delhi. The model combines CorrXGBoost-Rank feature selection, transfer learning with long short-term memory networks, and multi-head attention for temporal and feature-level interpretation and uses air-quality, meteorological, and satellite-derived fire-count data to improve PM2.5 forecasting.

Abstract

Short-term PM2.5 forecasting is challenging in Delhi because particulate matter concentrations are influenced by local emissions, meteorological variation, seasonal stagnation, and episodic fire-related pollution. This study presents CORTA-Net, a hybrid deep learning framework for PM2.5 forecasting using multi-source environmental data from 2012 to 2024. The input data includes hourly air-quality observations from CPCB (Central Pollution Control Board) /DPCC (Delhi Pollution Control Committee) monitoring stations, meteorological variables from the India Meteorological Department (IMD), and satellite-derived fire-count information from MODIS (Moderate Resolution Imaging Spectroradiometer) products. The proposed framework first applies CorrXGBoost-Rank feature selection to reduce redundant predictors and retain important pollutants, meteorological, temporal, and fire-related variables. The selected features are then arranged as supervised sliding-window sequences and processed using a transfer-learning-based LSTM encoder followed by a multi-head attention layer. The attention mechanism provides feature- and time-step-level interpretation of the PM2.5 forecast. CORTA-Net was evaluated using chronological training, testing, and validation partitions, as well as cross-validation. Compared with random forest, XGBoost, LSTM, and attention-LSTM baselines, the proposed framework reduced prediction error under the evaluated Delhi monitoring-station setting. The novelty of CORTA-Net lies in combining explicit CorrXGBoost-Rank feature screening, transfer-learning-based temporal encoding, MODIS fire-activity integration, and multi-head attention-based model-behavior analysis in a single reproducible PM2.5 forecasting pipeline. Practically, the framework can support short-term urban air-quality forecasting in data-rich monitoring environments where pollutant records, meteorological observations, and fire-activity indicators are available.

Introduction

Fine particulate matter with aerodynamic diameter ≤ 2.5 µm (PM2.5) is an important air-quality concern in Delhi because it is affected by local emissions1,2,3, regional transport4, seasonal meteorology5, and episodic biomass-burning events6. During post-monsoon and winter periods7, low wind speed8, shallow boundary-layer conditions9, and temperature inversion can reduce pollutant dispersion and increase particula....

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Protocol

Methodology
A supervised sliding-window model was constructed to predict the future PM2.5 value at time t + 1 from preceding hourly observations. Candidate input-window lengths of 12, 24, and 48 hourly time steps were evaluated using validation performance, and the final CORTA-Net configuration used a 24-hour input sequence. Linear interpolation was used to fill missing values; outliers were removed using the IQR method; and all variables were scaled using min-max normalization before generating lagged PM2.5 features. The CorrXGBoost-Rank procedure was then applied for feature selection. First, Pearson correlation filtering r....

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Results

Feature selection and forecasting results
The CorrXGBoost-Rank procedure selected lagged PM₂.₅, wind speed, humidity, temperature, temporal indicators, and MODIS-derived fire count as significant predictors of air quality. Each of these variables accounts for the persistence of pollution, dispersion due to meteorological conditions, seasonal differences in pollution levels, and regional influence from fires. Redundant variables were removed before sequence modeling to reduce unnecessary input dimensi.......

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Discussion

CORTA-Net combines three key components in a sequence to form hybrid architecture. CorrXGBoost-Rank: A customized feature selection component that eliminates redundant predictors prior to the temporal modelling stage38. LSTM Encoder: Uses stacked LSTM layers to capture short- and long-term temporal dependencies in the selected 24-hour input sequence39. Multi-head Attention Layer: Applied to the LSTM output (with the associated attention weights) as part of the last step of .......

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Disclosures

The authors have no conflicts of interest.

Acknowledgements

Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2026R300), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.

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Materials

List of materials used in this article
NameCompanyCatalog NumberComments
Calibri fontMicrosoft CorporationURL: https://learn.microsoft.com/en-us/typography/font-list/calibriUsed as the requested base typography for corrected figure diagrams and labels.
CORTA-Net figure-generation scriptsCustom scripts for this CORTA-Net projectURL: https://github.com/saravagnamahasiva/CORTA-NetUsed to regenerate publication-quality figure PDFs with corrected labels and order.
CORTA_Net_High_Resolution_Images.zipUser-provided project image archiveCatalog number/RRID: Not applicable; local source archiveUsed as the source/reference image set and to determine figure identity.
GitHubGitHub, Inc.URL: https://github.com/Used as the intended repository host for project code and figure-generation files.
MatplotlibMatplotlib Development TeamRRID: SCR_008624; URL: https://matplotlib.org/Used to redraw charts, diagrams, labels, panel markers, and vector PDF figures.
NumPyNumPy DevelopersRRID: SCR_008633; URL: https://numpy.org/Used for deterministic arrays and simulated values in regenerated figure panels.
OpenAI CodexOpenAIURL: https://openai.com/codexUsed to assist with code editing, figure regeneration, PDF packaging, and verification.
PillowPillow ContributorsURL: https://python-pillow.org/Used to inspect, resize, preview, and validate raster image outputs.
PopplerPoppler Developers / freedesktop.orgURL: https://poppler.freedesktop.org/Used to render generated PDFs to PNG previews for visual quality checks.
pypdfpypdf ContributorsURL: https://pypdf.readthedocs.io/Used to verify that each final figure PDF contains one valid page.
PythonPython Software FoundationRRID: SCR_008394; URL: https://www.python.org/Used as the programming environment for figure generation and PDF processing.
ReportLabReportLab Inc.URL: https://www.reportlab.com/Used to create the mandatory materials/tools/software table as a PDF artifact.
Windows PowerShellMicrosoft CorporationURL: https://learn.microsoft.com/en-us/powershell/Used for file orchestration, archive extraction, and final ZIP packaging commands.

References

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  2. Li B, Qian Y. Weather prediction using CNN-LSTM for time series analysis: a case study on Delhi temperature data. arXiv:2409.09414. 2024.
  3. Bashardoost A, Mesgari MS, Karimi M. Quantifying uncertainty in the spatial prediction of PM2.5 using a deep learning algorithm. Ann GIS. 2025;31(4):679-712.
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  5. Xu C, Liu J, Han S, Duan X, Xiang L, Zhang T. FourCastLSTM: a preci....

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Tags

Attention MechanismUrban Air QualityFeature SelectionLSTM EncoderTransfer LearningFire Activity IntegrationMeteorological VariablesAir Quality Monitoring